In recent years, communication networks such as the Internet of which information devices such as computers are becoming common at explosive pace. In particular, the Internet covers most of the world. A very large number of servers are connected to the Internet. A very large number of users are always accessing the Internet. Nowadays, it is almost impossible to know not only all servers connected to the Internet, but all users who are accessing the Internet.
On the Internet, information is transmitted through computers (i.e. servers, user computers, etc.) that function as nodes. As a method for accessing the Internet, the user should directly connect his or her server to the Internet. Alternatively, the user should contract with a so-called provider for an Internet connection service and then connect user's terminal unit to a server of the provider using a dial-up connecting method, leased line, data over cable, DSL, and/or other connection mechanisms (i.e. WiFi, etc.).
In addition, on the Internet, the user can upload data to a server for which he or she has contracted so as to publish information. As a means for publishing information to the Internet, web pages are known. Using web pages, Internet addresses from which data is published (these addresses are referred to as URL: Uniform Resource Locator) can be easily accessed. In addition, using for example FTP (File Transfer Protocol), directories that store data can be directly accessed. Still yet, data may be shared among users using “peer-to-peer” protocols.
In view of the vast number of servers and users on the Internet, illegal actions cannot be easily prevented. For example, using the various methods discussed above, it is quite common that unauthorized persons communicate copyrighted works and other digital assets that belong to another person without permission. There is thus a need to improve the manner in which copyrighted content and other digital assets are protected on various networks.